The present invention relates to a method and apparatus for the control of an excavating machine, particularly a cutter loader, in an underground excavation.
More particularly, the invention relates to that type of automatic control of the operation of a cutter loader wherein the face conveyor upon which the cutter loader is mounted serves to define an artificial horizontal serving as a reference for various aspects of the automatic control.
Particularly when the seam being cut is of relatively small thickness, for example 1 to 1.5 meters, control of the cutter loader under the direct supervision of a human operator is disadvantageous. If the human operator actually accompanies the cutter loader as the latter travels along the face, the human operator will not be able to stand upright and as a result may have considerable difficulty in observing the conditions which he must take into consideration in adjusting the height of the cutter; of course, the human operator may have great difficulty in obtaining access to so low a space at all. On the other hand, if the human operator controls the operation of the cutter loader from a more convenient distance, by radio remote control, it is evident that he will likewise not be in the best possible position to observe the face conditions which ideally should determine his control of the cutter height. Furthermore, in either event, reliance must be made upon the personal skill of the human operator of the cutter loader, and such skill is very difficult to develop.
Accordingly, attempts have already been made in the mining industry to provide for the automatic control of cutter loaders, in order to maximize the speed with which the cutter loader can excavate along the length of the face, and in order to maximize the amount of coal and minimize the amount of adjoining rock cut, and in order to create a reduced demand upon the skill of the human operator.
Particularly in the Eastern-bloc European countries and also in Great Britain (see for example "Bretby Broadsheet," July/September, 1968, No. 44, pp. 3-4), methods for the automatic control of the operation of cutter loaders have come into existence. With these methods, there is first of all established an artificial horizontal to serve as a plane of reference for the position and inclination of automatically operating cutting instrumentalities. Usually, the cutter loader is mounted for movement along the length of a face conveyor laid alongside the face being worked, and the face conveyor is utilized as the artificial horizontal.
With these known automatic-control methods, it is desired that the cutting roller be made to automatically follow the interface between coal and adjoining rock. In this way, supposedly, the cut will exactly correspond to the interface; or, in situations where the roof must be made of coal, the cut will be parallel to and spaced a predetermined distance from the interface. To detect the location of the coal-rock interface as the cutter loader proceeds along the face being worked, use is made of isotope test probes or measuring drill devices which can detect the difference in mineralogical or mechanical characteristics of the two different materials at the coal-rock interface. The heights of the cutter rollers of the cutter loader are automatically adjusted in dependence upon such detection, as the cutter loader proceeds along the face. It is also known to employ an inclinometer for detecting transverse tilting or climbing of the cutter loader. This transverse climbing is most often due to the accumulation of fines beneath the side of the conveyor adjoining the coal face. According to the known method, the known problem of compensating for the improper "climb" of the cut attributable to this factor involves, first, detection of the "climb" using the inclinometer and, second, adjustment of the position of the cutting instrumentality in such a manner that the "climb" of the entire arrangement not interfere with the ability of the cutter loader to accurately follow the coal-rock interface at the roof.
These known automatic-control expedients are not suitable for many situations. These prior-art expedients presume the existence of a relatively definite and continuous interface between the coal and the neighboring rock, and the absence of significant geological discontinuities and irregularities. Accordingly, whereas the prior-art expedients may be suitable where the geology actually corresponds to such assumptions, they do not work well for example in Western Germany, where the geology of the mining regions is such that definite and continuous coal-rock interfaces are often not encountered.
Where the coal-rock interface is not sharply defined, the automatic-control arrangements of the prior art will not be able to locate the interface and accordingly will have no basis for controlling the heights of the cutting rollers of the cutter loader. Where the coal-rock interface is highly discontinuous and/or irregular, the automatical-control arrangements of the prior art will react to every discontinuity and irregularity, resulting in unacceptably great overcompensation, or even complete inability to successfully follow the interface.